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How to divide dwarf iris

How to divide dwarf iris

Transplanting iris is a normal part of iris care. When well cared for iris plants will need to be divided on a regular basis. Many gardeners wonder when is the best time to transplant iris and how should one go about moving iris from one place to another. Keep reading to learn more about how to transplant iris.

Signs You Need to Transplant Iris

There are a few signs that you should consider dividing iris plants.

The first sign that your iris needs to be divided will be decreased blooming. Overcrowded iris rhizomes will produce fewer flowers than uncrowded iris rhizomes. If you have noticed that your iris are blooming less than they usually do, you may need to transplant the iris in your garden.

The next sign that you should consider transplanting your iris is if the rhizomes start heaving out of the ground. Overcrowded iris rhizomes will start to push on each other, which results in the entire root system of your iris plants literally pushing themselves out of the ground. The iris roots may look like a mass of snakes or a pile of spaghetti when they need to be divided. They may even stop putting up foliage and the plants may only grow foliage on the outside edges of the clump.

When to Transplant Iris

The best time when to transplant iris is in the summer, after the iris have finished blooming, up until fall.

Steps for Dividing Iris Plants

To divide your iris, start by lifting the clump of iris plants out of the ground with a spade or fork. If possible, lift the whole mass out whole, but if you are unable to do this, carefully break the clump into smaller parts and lift these out.

Next, brush of as much dirt as possible from the iris rhizomes. This will make it easier to see when you are breaking the clumps apart.

The next step in dividing iris plants is to divide the iris rhizomes. Each iris rhizome should be divided into pieces that are 3 to 4 inches long (8-10 cm.) and have at least one fan of leaves on the rhizome. Do not remove the roots from the rhizomes.

As you get closer to the center of the clump, you may find large sections of rhizomes that have no leaf fans. These can be discarded.

Check all of the divided iris rhizomes for iris borers and disease. The iris rhizomes should be firm and not soft. If the rhizome feels soft, throw it away.

Steps for Transplanting Iris

Once the iris rhizomes have been divided, you can replant them. First, trim all of the iris leaf fans back to about 6 to 9 inches tall (15-23 cm.). This will allow the plant to re-establish its roots without having to support a large amount of foliage at the same time.

Next, plant the iris rhizomes in the selected location. This location should receive a good deal of sunlight and should be well draining. Dig a hole where the rhizome will settle into the ground just below the ground level. If planting several iris near each other, point the rhizomes away from each other and space them 18 inches (46 cm.) apart.

Spread the roots out around the rhizome and then cover the roots and the rhizome with dirt. Water the newly transplanted iris plants well.

Irises can be kept healthy and full of flowers by dividing clumps before they get congested. This is also a good way to increase stocks of plants.

Quick facts

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  • When to divide irises
  • How to divide irises
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Suitable for.

Both clump forming irises and those with rhizomes (fleshy stems at soil level) can be divided. Irises that are grown from bulbs are not suitable for division.

When to divide irises

How to divide irises

Bearded rhizomatous irises

Bearded irises (sometimes sold as Iris germanica cultivars) have large fleshy stems (rhizomes) at soil level and flowers with soft hairs (the ‘beard’) on their lower petals (falls).

  • Lift and divide rhizomatous bearded irises every three to five years
  • This is ideally carried out six weeks after flowering, to give sufficient time for the plants to produce new growth for the following season before they enter winter dormancy

Division:

  • Cut away each fan of leaves from the clump, using a sharp knife. Each fan should have a portion of young rhizome (up to 15cm/6in long for tall bearded irises, smaller for miniature tall bearded irises)
  • Select the largest fans with the healthiest rhizomes
  • Discard smaller fans and old, withered looking rhizomes
  • Shorten the leaves to about 15cm (6in) above the rhizome and trim the roots to shorten them

Replanting:

  • Dig a hole, large enough for the rhizome and roots, mounding the soil slightly if this makes placing the rhizomes easier, but otherwise working the soil back between the roots
  • The rhizome should be placed at soil surface on heavy soils, but a little below the surface on light sandy soils, as they will work their way back to the surface
  • Replant the divisions in groups, with 30cm (12in) between larger plants and 15cm (6in) between dwarf plants

Siberian irises

Siberian irises are clump-forming irises with beardless flowers. Large clumps can be divided to rejuvenate them if flowering has become reduced at the centre of the clump.

  • Divide large clumps shortly after flowering, using two forks inserted back to back in the centre of the lifted clump
  • Remove any old rhizomes and roots; avoid breaking the clump into small sections
  • Replant the younger outer sections to the same depth as they were planted before

Unguicularis irises

Iris unguicularis are low-growing clump-forming irises with beardless flowers that flower in late winter and early spring. Large clumps can be divided to rejuvenate them if flowering has become reduced at the centre of the clump.

  • Divide clumps in autumn, or wait until after flowering has finished in spring
  • Use your hands to pull apart the divisions, or, if this is insufficient, try two hand forks inserted back-to-back in the centre of the lifted clump
  • Split the clump into largish sections to avoid disturbing the roots excessively
  • Replant the divisions to the same depth as they were planted before

Pacific Coast irises

Pacific coast irises are low-growing clump forming irises with beardless flowers and grass-like leaves. Large clumps can be divided to rejuvenate them if flowering has become reduced at the centre of the clump.

  • As these irises dislike root disturbance, lift only part of the clump in autumn (the best time) or in late spring once new roots have appeared
  • Take divisions from the healthy and vigorous areas at the edge of the clump, replanting them to the same depth as they were planted previously

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Table of Contents

When can you split mini irises?

However, they can be divided at any time from six weeks after they have finished flowering. Bearded irises are best divided when the clump is large and the rhizomes in the middle of the clump are starting to get congested.

How do you divide dwarf iris?

  1. Dig up the entire clump with a garden fork or split off individual rhizomes.
  2. Remove excess dirt and dead material from the clump.
  3. Trim the leaves down to 4-6”.
  4. Break apart the rhizomes from the clump by using your hands or a knife.

Do you cut back dwarf iris?

Plant the bulbs in a sunny site with well-drained soil in the fall. Dwarf iris plants are hardy to Zone 5 and naturally bloom in early spring. Just allow them to grow this season, they will die naturally, trim them back and save the bulbs.

Do dwarf irises multiply?

Over time, if planted in the ground, these bulbs will multiply and get congested, at which point dig them up in late summer and divide them before replanting.

Can you move irises in the spring?

A: August or September is the best time to divide and transplant irises, but you still can transplant them now. Your irises may not bloom this spring. Start dividing them by removing the entire iris clump. To make the rhizomes easier to handle, reduce the length of the blade foliage by half.

When can you dig up iris bulbs and replant them?

The best time when to transplant iris is in the summer, after the iris have finished blooming, up until fall.

Can you transplant irises in the spring?

How long do dwarf irises bloom?

Since each flower last between 3-7 days, the gradual succession of buds means that these Dwarf Irises will flower for around three weeks. With pretty colors, elegant forms and striking markings, they are a wonderful way to welcome spring to our sleeping winter gardens.

Do I deadhead irises?

Irises may benefit from shallow mulching in the spring. Deadhead (remove spent blooms) consistently; Bearded Irises will flower sequentially on buds spaced along the stems. After blooming is finished, cut flower stems down at their base, but do NOT trim iris leaves after they have finished blooming.

How long do dwarf irises bloom for?

What happens if you transplant irises in the spring?

But, as iris rhizomes spread, they become crowded. This stresses the plants and can even cause them to stop blooming and become susceptible to pests, such as iris borers. By dividing and transplanting your irises, you will rejuvenate the plants and be rewarded with a greater number of healthy blooms in the spring.

When should irises be divided?

Bearded irises should be divided every three to five years, as the plants quickly become overcrowded and don’t bloom well. July or August is the best time to dig, divide and transplant bearded irises.

When to divide and transplant Iris?

The best time to divide and transplant Iris rhizomes is 2-3 weeks after the finish of blooming.

When to thin and transplant irises?

A. Iris beds need “thinning” periodically (every two or three years). September is the ideal time to plant or to divide and replant iris – the common man’s orchid. Here’s how it’s done.

How often to divide Iris?

In general, divide your iris plants every three to five years as the clumps get large. If you notice the plants stop flowering as well as they once did or appear crowded, it is likely time to divide and replant.

By Beckie Fox Filed Under: Garden Newsletter

During the dog days of summer, gardeners are mostly trying to keep on top of routine tasks: deadheading annuals and perennials; weeding; watering containers and vulnerable plants; and maintaining the compost pile. But if you grow bearded irises, add “divide iris rhizomes” to your to-do list.

For the why, when and how of this annual task, read “Dividing irises” from Penn State Extension Service and “How to divide iris” from Savvy Gardening for solid advice. If you want a visual lesson, here’s a YouTube video prepared by Toronto Master Gardeners.

Now is also the time to strike a couple of tasks from your to-do list. It’s time to stop supplemental feeding of trees and shrubs, because the resulting new growth may not have time to toughen up before winter strikes. It’s also best to avoid moving or dividing herbaceous perennials or seeding a new lawn when it’s hot and dry. Better to do these projects in the fall, when temperatures are usually cooler and there is the likelihood of more rain. (Sadly, that’s not often the case nowadays, but we can hope.)

Designing with small ornamental grasses

Not everyone has room for the tall, dramatic ornamental grasses so popular these days, nor does everyone relish the task of bushwhacking big clumps down in late winter/early spring to make room for next season’s growth. But if you want the texture and form that ornamental grass can provide in a perennial bed or a low-maintenance partner for hostas, consider a few of the shorter varieties, such as moor grass and dwarf fountain grass. In “Benefits of short ornamental grasses” Judith Adam lists a few of her favourites.

World’s smartest insects

Have you every wondered what the most intelligent insect is? Maybe not, but people at Atlas Obscura posed this question to a few entomologists. Of the many insects to consider, I’ll narrow your options down to three to give you a head start. Is it ants, honeybees or cockroaches? Here’s the verdict.

Published: August 20, 2021 | Updated: August 30, 2021

About Beckie Fox

Beckie is Editor of Garden Making. She is a Master Gardener and published author in Niagara-on-the-Lake, Ontario.

How to divide dwarf iris

Dwarf Iris flowers are one of the first types of blooms to announce the start of Spring. They are compact plants that reach only 6 inches tall, and grow in shades of blue and yellow. Danfordiae is the only yellow dwarf iris variety. The Reticulata varieties have more varied shades and also a delightful fragrance. Dwarf Iris are a breeze to grow and naturalize and multiply easily.

Planting dwarf iris bulbs:

    In the Fall, choose a spot that gets quite a lot of light and has good soil drainage.

Planting dwarf iris bulbs is fairly simple. You’ll notice when you receive your bulbs that they look like mini onions and it will be easy to see that the spike should point upwards when planting.

Usually the rule of thumb when planting bulbs is that bulbs need at least 2 times their height of soil above them. Dig a 2 to 3 inch deep hole, drop the bulb into it (remember, spike points up!) and cover with soil.

Regarding spacing between bulbs, if planting in beds, leave approx 4 inches between each bulb. If you are planting in containers, you can cluster them a little closer together.

After planting, water well so that the soil above the bulbs settles.

  • Dwarf Iris bulbs will flower in the early Spring. After the flowers die down, the plant can enjoy a warm rest period. You don’t have to water too much during this rest period. Leaves will also die back and start to yellow. At this point, you can choose to tidy up the plant and remove the old leaves.